Gas turbine engine frame structure



March 20, 1956 H. c. HILL 2,738,647

GAS TURBINE ENGINE FRAME STRUCTURE Filed July 5, 1951 3 Sheets-Sheet l A 7709M; Y5

March 20, 1956 H. c. HILL AS TURBINE ENGINE FRAME STRUCTURE Filed July 3 1951 3 Sheets-Sheei 2 JNVENTOR. A E/VEV a H/ZL March 20, 1956 Q GAS TURBINE ENGINE FRAME STRUCTURE 3 Sheets-Sheet 3 Filed July 5, 1951 United States Patent 2,738,647 GAS TURBINEENGINE FRAME STRUCTURE Henry-C. Hill;- Seattle, Wash, assignorto BoeingAirplane Company; Seattle, Wa'sln, a corporation of Delaware Application July 3, 1951, Serial No. 234,997 7Cliiii'ns. (Cl.60'39.08)

This invention relates" to frame structures for gas turbineengin'e'sand' is directed to improvements increasing tliefo'rmeradvantage of such engines ov'er reciprocating types in respect to simplicity, light weight, small volume, vibration freeop'eration; and other factors of merit.

The'ga's" turbine engine, involving extremely high operating" temperatures, bodies. rotating at tremendous speeds and the requirement that a relatively lightweight, small engine structure develop relatively high torque presents serious design problems many of which are relativel'y'new' in the field of engine design. While much progress has been made in the perfection of such engines for commercial. and" military usage certain problems remain'etl'to be solved. One such problem experiencedinvol'vedvibra'tion resonance in the frame. At' the tremendous rotational speeds of the turbine and compressor wheel s, namely in the vicinity of 36,000 R. P. M., previous types of frame structures exhibitcd complex modes of vibration which probably could'be eliminated, if at all, only by inconvenient mounting arrangements together withconsiderable' increase in the mass and bulk of the frame" to achieve the necessary strength and rigidity in all'p'lane's' of stress and vibration.- Moreover, dynamic deflections and"misa'lignments were observed between the twomajor engine sections, namely the gas producer and the"pow'er"outputsections, caused by high and variable torque loadings; These also seem to depend for a solution upon a h'eav'ie'r and bulkier frame. However, asgas turbine" en'gi'nes" otherwise satisfactory. in most respects cana'nd' ha'vebeen" built at approximately onefourth the volume'aindone seventh the weight of conventional diesel engines of comparable horsepower,-for instance, an impr'oVedfi'a'me"structurebecame an important goal, especially formotorvehicle a'ndlike applications;

An object" of the present invention, therefore, is to eliminate vibration resonance and torque' defiection conditions in engines of the gas turbine type by providing an improved framestructure, of'minimum weight and size, andof simple, convenient design, solvingthese-problems. Arelatedbbjectissucli'an engine frame which permits arranging tlieengi'ne' parts for greater compactness and easier accessibility to"the"variou's parts. Furthermore it was' a"purposetoprovidea; frame arrangement'aifording natural shielding 'ofthe' more heat vulnerable accessories of the engine against the intense radiation of heatfrom theturbineno'znebex.

Another object of the invention is a gas turbine" engine frame adapted for installational mounting. in a manner and by an arrangement of' suspension mounts further minimizingvibrationresonance conditions and torque displacements: I

Stillanotherand important object is an engine frame structure" achieving? the foregoing" objectives and utilising main: strtictilralelements in the additional capacity of armor eftectiveto'prote'ct bynantling personnel and equip mane against possible dan ers from a bursting: turbine wheel? Under previous concepts of engine frame design the startingpoint was the provision of a generally. flat bed or base upon which the various engine componentswer'e mounted by and betweenupriglit frame'parts, a type of design entirely befitting reciprocating engines. Rigidity an'd'strength ofthelfrarne as awhole informer practice was achieved mainly by virtue of massandsiz'e' of'th'e base, supplemented in the instance of the reciprocating .engineby the inherent rigidity of a cylinder block and head extending the length of the main section or power unitofthe engine;

However, in the case ofa gas tuIbineengine'the generally' fiat base alone in the former framedesign practice was the major source of rigidity and strength in the frame, as the turbine casing by which the two major'opcrating sections or the engine are joined is of relatively thin metal" subjected to' extremely high temperatures, hence did not add'greatly to structural rigidity in the frame. Under torque loading between the gas producer and power output sections of the engine,v the relative fiatriessand offset position of the base relative to the engine axis precluded effective resistance to torque deflections between the two sections. Increasing, the depth and "mass ofthe base added undesired volume andweight t'o'the engine asthe price to pay for greater rigidity in thefrarne. It also increased the dissymmetry of the al ready'unsymtnetrical frame structure, which studies leading' to the present invention found to sustain complex modesof vibration resulting inframe resonance. Moreover, theonlyfeas'ible arrangements of-engine suspension mounts'with previous frames were unsymmetrical. and fiirtlier cohtributed tovibration and torque deflections.

In accordance with the present invention the engine frame structure herein disclosed comprises longitudinal members, preferably three in number and of tubular form, Which extend between symmetrically arranged anchor points on the respective engine sections and-are bridged and stiffened transversely by reinforcing plates; The triangularly arranged'reinforcing plates also serve as armor, jacketing the turbine housing to protect bystand* ing persons andob'je'cts against possible dangers from bursting turbine wheels.- Because of its special form the weight of such a frame structure is low in relation-to its stifines's and resistance to vibrations.

symmetrically arranged suspension mounts located near theoutput'e'ndof the engine enable supporting the same in a manner conducive to vibrationless operation and minimumtorque' deflections.

Formerly, it'wa's the practice to mountthe accessory compdnents'u'pon an engine frame header located at the compressor libhsir'igLend of the engine, and relatively unprotecte'dfro'm the? intense heat radiation from the turbinenozzle'box. Another feature of the improved frame structure" herein described is the mounting. of the triangularly arranged longitudinal frame memberspreviously mentioned'between the output gear housing and'an intermediately located-frame partition which surrounds the compressbrsh'aftata location next to the turbine housing au'cl isstrdcturally integrated with the gasproducing sec tionofth'e en'gine. This structural partitionserves as'a heat 'shieldingmountfor the the auxiliary components-and also asa" casing. for power take-off gearing driving. the samefromthe compressor-shaft.

The'foregoing and other features, objects and advan-x tages of the invention. will-become more fully evident from the following detailed descriptionof the presently preferred form' of gasturbineengine frame structure embodying. the invention, as illustrated in the accompanying drawings;

Figure 1 is a perspective view of an engine income ratingithe improved 'ftame structure.

Figure 2 is a longitudinal sectional view of the same with parts broken away to illustrtae certain details.

Figure 3 is a transverse sectional view taken on line 3-3 in Figure 2.

Figure 4 is a transverse sectional view taken on line 44 in Figure 2.

In Figure 2 that portion of the engine lying generally to the right of the dotted line A-A constitutes the power output section of the engine, and that to the left of the line the gas producing section thereof. The power output section includes the power output shaft 10, the power output gear box 12 and the main power turbine wheel 14 which develops the power for driving the shaft through gear unit 12. The gas producing section of the engine generally comprises the air compressor 16, the first-stage turbine 18 driving the air compressor by means of the shaft 20, the nozzle box 22, the burner ducts 24 interconnecting the nozzle box and air compressor, and the auxiliary components and mount 26.

At the head end of the engine, air is admitted into the compressor 16 through a throat 28 and by centrifugal pumping action of the vaned wheel 30 is driven into the annular collector chamber 32. The compressed air is led off through two elbow ducts departing tangentially from the collector chamber to take advantage of the circumferential velocity of air therein caused by rotation of the centrifugal pumping wheel 30. The two elbow ducts 34 carry the air into the burner chambers or ducts 24 in which fuel is injected by suitable nozzles (not shown) for combustion purposes. The hot gases of com- I bustion pass into the turbine nozzle box 22 extending annularly around the hub of the turbine wheel 18. Such gases then flow parallel to the turbine axis through turbine nozzles 36 directed against the blades of the firststage turbine 18. Power is thus generated to drive the air compressor wheel 30 by means of the shaft 20.

A system of lubrication is illustrated in Figure 2, which is disclosed and claimed in my copending application Serial No. 246,887, filed September 17, 1951, now Patent No. 2,676,458. Briefly, the lubricant, which in that system is also the fuel, is delivered by a pipe 38 to the hollow interior of a receptacle 4% located at the hub of the compressor wheel 30. The hollow compressor shaft 20 receives an elongated dirt collector tube 42 extending substantially throughout the full length of such shaft. This tube carries an inlet nozzle 44 which enters the receptacle to admit lubricant therefrom into the interior of the tube. The nozzle is appropriately journaled and sealed against leakage in the inner end of the receptacle. of the tube 42 therein, subjects the lubricant in the tube to high centrifugal force causing dirt particles and other relatively heavy foreign elements to be flung radially outward and remain against the wall of the tube, while the lighter and purer lubricant remains in a central core region in the tube. This core fluid is drawn off by tap tubes 46 and 48 acting as individual centrifugal pumps to lubricate the respective antifriction bearings 50 and 52, by which the compressor shaft is rotatably supported in the engine frame journals 54 and 56, respectively.

At the turbine end of the tube 42 the closure plug 58 has a central aperture 60 through which the pure lubricant at the center of such tube is admitted into the inlet of a centrifugal pump. This pump is formed by a central bore 62 and a plurality of communicating radial bores 64 in the hub assembly of the turbine 18, comprising the flanged end 20' of the compressor shaft 20 receiving the stub shaft iii, of the turbine 18. An annular collector duct 66, formed in the hub bearing assembly, receives the lubricant pumped by the radial bores 64 and delivers it to an outlet pipe 68 which, as explained in said copending application, delivers such lubricant to the output gear unit 12 by means of pipe 70, and, as fuel, to the engine burners (not shown).

After passing the first-stage turbine wheel 18, the hot The high speed of rotation of the shaft 20, hence I i gases in the turbine casing annular duct 72 are directed against the main power turbine wheel 14 and ultimately out into the atmosphere through the exhaust ducts 74.

In accordance with the present invention the power output and the gas producing sections of the engine are supported in fixed relation to each other by a frame structure comprising three triangularly arranged longitudinal frame members 76 disposed symmetrically with relation to the longitudinal axis of the engine. As shown in Figures 1 and 2 the right-hand ends of these tubular frame members 76 are rigidly, but removably, fastened to the radial arms 78 projecting in equilateral positions from the output gear housing 12. The opposite or left-hand ends of the frame members 76 are correspondingly connected to the respective three corners of a generally triangular frame partition 80 located adjacent the turbine nozzle box 22. Such transverse partition also serves as a housing for auxiliary component drive gearing and as a mount for the auxiliary components, including startergenerator unit 88, booster pumps (not shown), tachometer (not shown) and others.

The frame members 76 are preferably of tubular form, while the radial frame arms 78 and drive gear housing 80 are likewise of hollow construction. As a result, maximum strength and rigidity of these interconnected frame components is achieved with minimum weight, and their interiors may be placed in communicatioin with one another to provide oil and vent passages between the first and second sections of the engine. The interconnected members 76, 78 and 80 form a rigid structure which is symmetrical in relation to the engine axis and offers the requisite degree of stiffness between the two major sections of the engine against vibration, torque deflection, and other longitudinal and transverse components of strain.

The main frame structure interconnecting the two engine sections is completed by the triangularly arranged web plates 82 bridging between the frame tubes 76 in the manner shown and removably connected thereto. The width of such webs parallel to the longitudinal axis of the engine is about half the length of the frame tubes 76, although the dimension is not critical. Such reinforcing plates greatly increase the torsion resistance of the frame, and generally stiffen the frame structure against transverse vibrational tendencies and bending.

The removable connections of the members 76 to the arms 78 and housing 80 and the removable connections of the web plates 82 to the members 76 facilitate disassembly and of maintenance and repairs on the engine.

The frame web plates 82 arranged in prismatic form are preferably of structural steel. Although these plates form a jacket surrounding the turbine casing, they are not heated as greatly during operation of the engine as the turbine casing because of the air circulation permitted between such plates and the turbine casing, and because of direct radiation occurring from the plates. Consequently, their desired rigidity may be achieved without making them abnormally thick. Because of their encompassment of the turbine wheels, the plates 82 serve as armor guarding against possible dangers from a bursting turbine wheel. The fragments of a bursting turbine wheel breaking through the turbine housing would strike the Slates and merely ricochet around the space between That portion of the frame structure comprised in the gas producing section of the engine is likewise generally symmetrical in relation to the engine axis. The generally triangular gear housing 80 is rigidly connected to the compressor housing by a sleeve 84 surrounding the compressor shaft 20 and supporting the journals 54 and 56 in which such shaft rotates. Radial rib plates 86 at degree angular spacing on the sleeve 84 interconnect and brace these two housings. In the sectoral spaces between plates 86 the various engine auxiliary components are respectively mounted, including the starter-generator 88 and others supported directly by the partition structure 80 on the side thereof away from the turbine nozzle box. The various auxiliary components are thus grouped in generally symmetrical fashion around the relatively smalldiameter sleeve 84 generally within the outline of the engines frame structure, hence do not impair the overall compactness of the engine. Moreover, being arranged as they are about sleeve 84 such components are easily accessible for installation and removal.

The partition structure 80 serves as a main structural portion of the frame, as a housing for gearing 90 by which the ditferent auxiliary components are driven from the compressor shaft, and as a support carrying the auxiliary components in convenient locations and in compact arrangement, also serves the important function of a heat shield preventing destructive heat radiation reaching the diiferent auxiliary components from the intensely heated turbine nozzle box 22. These components are not greatly heated by the adjacent burner ducts 24, as temperature in the shells of these ducts is relatively low because of coolness of air received therein from the compressor.

Three engine rubber suspension mounts 92 at symmetrical locations on the respective reinforcing plates 82, and near the power output end of the engine, provide a suspension mounting for the engine which minimizes vibrations and torque displacements of the engine as a whole in relation to the supporting structure in which it may be mounted.

Itwill be noted in the drawings, and especially in Figures 3 and 4, that there is a slight dissymmetry in the arrangement of tubes 76 relative to the engine axis. This is necessitated in the particular engine represented in order to afford clearance for the two burner ducts 24. However, the slight amount of unbalance resulting therefrom in the frame structure is not objectionable from the standpoint of vibration or otherwise. The term symmetrical, therefore, includes symmetrical and substantially symmetrical forms and arrangements.

I claim as my invention:

1. The frame structure for gas turbine engines having a power output section generally aligned axially with a gas producing section, said sections lying generally at opposite ends of the turbine housing interconnecting them, said frame structure comprising generally radially extending rigid frame portions on each of said engine sections and arranged generally symmetrically in relation to the engines longitudinal axis, and a plurality of transversely spaced longitudinal frame members rigidly interconnecting said respective frame portions and arranged in generally symmetrical pattern with relation to said axis, around the turbine housing, said power output section and gas producing section having a common lubricating means requiring flow of fluid between such sections attending lubrication thereof and the longitudinal frame members are of tubular form whereas the rigid frame portions have hollow interiors communicating with the interior of at least one such tubular frame member to constitute a passage sustaining said flow of fluid between the engine sections.

2. A frame structure for gas turbine engines having a power output section and a gas producing section generally aligned axially therewith, said sections lying generally at opposite ends of the turbine housing, said frame structure comprising generally radially extending rigid frame portions on each of said engine sections substantially symmetrical about the engines longitudinal axis, a plurality of transversely spaced longitudinal frame members of tubularrform rigidly interconnecting said respective frame portions and grouped symmetrically about the the sides of the turbine housing to protect against danger of outwardly thrown fragments of a bursting turbine wheel, said web members being removably connected to the res pcctive longitudinal frame members, and said longitudinal frame members being removably connected to the radially extending frame portions.

3. A frame structure for gas turbine engines having a power output section and a gas producing section generally aligned axially therewith, said sections lying generally at opposite ends of the turbine housing, said frame structure comprising generally radially extending rigid frame portions on each of said engine sections substantially symmetrical about the engines longitudinal axis, a plurality of transversely spaced longitudinal frame members rigidly interconnecting said respective frame portions and grouped symmetrically about the engines longitudinal axis, a plurality of reinforcing structural web members of plate form rigidly interconnecting the respectively adjacent frame members and being of a width measured longitudinally of the engine sutficient to strengthen the frame structure materially against torsion deflection between engine sections and at the same time provide a jacket surrounding the sides of the turbine housing to protect against danger of outwardly thrown fragments of a bursting turbine wheel, and a plurality of engine suspension mounts supporting and fixedly connected to the respective web members, intermediate the respective longitudinal frame members, said mounts being substantially coplanar and adapted for external connections to support the engine thereby.

4. The frame structure defined in claim 3, wherein the web members are substantially flat and are removably connected to the respective longitudinal frame members.

5. The frame structure defined in claim 4, wherein the longitudinal frame members are of tubular form removably connected to the radially extending frame portions.

6. The frame structure defined in claim 3, wherein the longitudinal frame members are three in number arranged at equal spacings about the engines longitudinal axis, and the web members comprise three substantially flat plates interconnecting said frame members.

7. The frame structure defined in claim 3, wherein the power output section and gas producing section have a common lubricating means requiring flow of fluid between such sections attending lubrication thereof, and the longitudinal frame members are of tubular form whereas the rigid frame portions have hollow interiors communicating with the interior of at least one such tubular frame member to constitute a passage sustaining said flow of fluid between the engine sections.

References Cited in the file of this patent UNITED STATES PATENTS 880,458 Krause Feb. 25, 1908 1,365,275 Robinson Jan. 11, 1921 1,986,435 Heinze Jan. 1, 1935 2,529,958 Owner et al. Nov. 14, 1950 2,539,960 Marchant et al. Jan. 30, 1951 2,591,399 Buckland Apr. 1, 1952 FOREIGN PATENTS 590,419 Great Britain July 17, 1947 

